The Biostatistics Core (Core C) will bridge the transition from the DIAN database stored and managed by the Informatics Core (Core H) to the analyses of the longitudinal data within, between, and among the various data domains, the latter of which serves as the primary responsibility of the Core. Specifically the Biostatistics Core will: (1) oversee the statistical quality control of data for the study and produce appropriately de-identified and statistically analyzable datasets for distribution/analysis; (2) lead the statistical data analyses and collaborate in report preparation for all Cores and projects, and consult on the design of all projects and on the application of appropriate statistical and methodological techniques; (3) develop and implement appropriate statistical models for longitudinal changes in potential markers and use these models to test the statistical hypotheses about the preclinical changes of AD and about the temporal difference on preclinical changes of AD among various markers, and (4) serve as an advisory group for other researchers interested in using the DIAN database for additional analyses. The Biostatistics core will achieve these specific aims through extensive interactions and collaborations with all other components of DIAN.